1. Field of the Invention
Embodiments of the present invention relate to electrical sockets for electrically and physically connect microelectronic device(s) to a substrate. In particular, an embodiment of the present invention relates to compressible domed contacts within electrical sockets to achieve effective electrical connection between the electrical socket and the microelectronic device.
2. State of the Art
Electrical sockets may be used to secure microelectronic packages and/or integrated circuit devices, electrically and physically to a substrate, such as a system board, motherboard, or a printed circuit board, of an electronic system. These electrical sockets circuit devices, such as microprocessors, ASICs, and memory chips.
The microelectronic packages, which are used in conjunction with electrical sockets, are generally grid array packages. In a grid array package, the input/output elements placed on the surface of the microelectronic devices. The grid array packages have many advantages, including, but not limited to, simplicity, high contact density, and low inductance due to the short paths between the contact and the element within the microelectronic device. There are several types of grid arrays, including ball grid arrays, pin grid arrays, and land grid arrays. Ball grid arrays and chip scale packages having hemispherical solder balls as input/output elements. Pin grid arrays have pins, as input/output elements. Land grid arrays have flat pads as input/output elements.
An exemplary electrical socket 402 is shown in FIGS. 16 and 17 adjacent a first surface 404 of a substrate 406, wherein the electrical socket 402 is physically attached to and in electrical contact with the substrate 406 through a plurality of solder balls 408. The solder balls 408 extend between bond pads 412 on or in the substrate 406 and respective substrate ends 416 (see FIG. 17) of socket contacts 418 (generally by a metallization layer 414). The substrate bond pads 412 are connected through traces 422 (represented by dashed lines in FIG. 17) to other components (not shown). The socket contacts 418 extend through a socket interface portion 424 of the socket 402 and contact respective lands 426 on an active surface 428 of a microelectronic package 432. The microelectronic package 432 is generally biased toward the interface portion 424 by a variety of mechanisms, such as springs, clips, and the like (not shown), as will be understood to those skilled in the art. The electrical socket 402 may include sides 434 abutting the socket interface portion 424 to form a recess in which the microelectronic package 432 may reside.
As shown in FIG. 17, the socket contact 418 includes the socket contact substrate end 416 and an opposing package end 438. The socket contact 418 may include a resilient finger 442, which contacts, and preferably is biased against, the microelectronic package land 426. However, co-planarity problems with the microelectronic package land 426 (e.g., varying thicknesses thereof) can result in a “no connect” (shown within the dashed circle in FIG. 18), wherein the resilient finger 442 does not contact the microelectronic package land 426, or only making “light” contact with the microelectronic package land 426, which result in an “intermittent” connection. The only means to over come these co-planarity issues is to increase the force of the bias of the microelectronic package 432 against the resilient fingers 442. However, such increased bias can have detrimental affects on the microelectronic package 432, as will be understood by those skilled in the art.
Therefore, it would be advantageous to develop a socket contact which is capable of consistently forming an effective electrical contact with the lands or bumps of a microelectronic package regardless of co-planarity issues within tolerance limitations.